1. Field of the Invention
The present invention relates to a running performance control apparatus suitable for use in an electric vehicle, which is capable of determining, based on a driver's choice, whether the running performance of the vehicle while being driven should be restricted when the capacity of a battery used for the running of the electric vehicle is reduced to a predetermined value.
2. Description of the Related Art
It has recently been pointed out that the environment is deteriorating due to noise and exhaust gases produced by gasoline vehicles. Therefore, a strong demand is now arising for wide use of electric vehicles as a countermeasure for solving such environmental problems.
Since this type of electric vehicle is normally driven by electric energy stored in a battery, the vehicle is provided with a large battery. However, the continuous running distance over which tile electric vehicle can be driven by one charge level is shorter than that obtained by a gasoline vehicle. Therefore, a method of efficiently using the capacity of a battery is an important consideration.
When a battery develops trouble and electric power outputted from the faulty battery is reduced, for example, an electric vehicle is apt to abruptly stop running before it reaches a desired destination when the electric vehicle runs under the action of the electric power outputted from the battery which is at fault.
In order to solve such a problem, a technique for comparing a normal battery voltage with an actual battery voltage in view of improper variations in the battery voltage due to a failure in a valve, and for determining a torque command value for a motor based on the result of the comparison so as to reduce the torque outputted from the motor, thereby making it possible to increase a vehicle drivable distance under the action of the defective battery, has been disclosed in Japanese Patent Application Laid-Open Publication No. 63-77302, for example.
However, the method which is employed in the above prior art has the problem that the running state is not controlled to provide the running state corresponding to the running environment at all times because whether the running environment of a running vehicle falls into either an express highway or an urban district area has not been taken into consideration.